1. Field of the Invention
The present invention relates to a varistor integrally comprising a resistor and a varistor element.
2. Related Background Art
Varistors are used in, for example, controlling devices, communication devices and their parts, to absorb or eliminate external surges (abnormal voltage) such as static electricity or noise, for protection against such external surges or noise.
The use of zinc oxide as a major component and rare earth elements, calcium oxide and silicon oxide as accessory components has been proposed for the constituent components of varistor elements in varistors, in order to enhance the varistor characteristics such as voltage non-linearity, as well as the discharge withstand current rating (see Japanese Patent Publication No. 3493384, for example).
Serial connection of resistors in a varistor requires separate mounting of two elements on the printed board, and thus increases the mounting space and conflicts against high-density mounting. Varistors that integrate varistor elements and resistors have been proposed as means for realizing high-density mounting (see Japanese Patent Publication No. 3097332, for example).